1. Field of the Invention
The present invention relates to a method and apparatus for measuring solder bumps formed on a semiconductor module such as LSI, on TAB (Tape Automated Bonding), and the like.
2. Description of the Related Art
FIGS. 1A to 1C illustrate the structure of a semiconductor module 1 having a number of solder bumps. FIG. 1A is a diagram showing the overall structure of the semiconductor module. FIG. 1B is an enlarged view of a bump area A of the semiconductor module and illustrates a relative position of solder bumps. FIG. 1C is an enlarged view of a bump 10 (corresponding to .beta. in FIG. 1A).
A number of solder bumps 10 are formed on the bottom of the semiconductor module 1. Each bump is used for connection to a wiring board on which the semiconductor module 1 is mounted. The semiconductor module 1 is of a square shape having a side length of, for example, 10 mm. Solder bumps 10 are formed on the surface 8 at a pitch of, for example, 450 .mu.m, totalling in number to 23.times.23.
Each bump 10 is generally spherical as shown in the enlarged view of FIG. 1C.
There is no apparatus for automatically measuring a height of a number of spherical bumps to date. Therefore, height is measured visually by using a focus-of-depth microscope or the like.
Works (to be measured) such as semiconductor modules formed with a number of bumps are positioned at a later process on a wiring board, and bumps are heated and melted in a heating furnace to be connected to the wiring board.
In order to reliably connect the bumps, it is necessary to correctly measure a height of each bump at its apex.
The size of each bump is required to have predetermined values so that adjacent bumps and wiring connections are prevented from being electrically shorted.
However, it is very difficult to measure heights of a number of bumps correctly and in a short time.
One of the inventors of this invention has proposed techniques of measuring a height of a work by using an optical beam, as disclosed in JP-A-2-80905.